The present invention relates to ventilator control systems and more specifically relates to the continuous control of an attic ventilation fan.
The advantages of ventilating the attic space above a dwelling have been known for a long time and it is often been the practice to provide wind-operated ventilators or the like to evacuate the air from the attic. More recently, thermostatically controlled power ventilators have been utilized which employ a thermostatically controlled electric fan to evacuate the air. Such power ventilators may be located at the end of the attic at the eaves or simply located in the middle of the roof with flashing providing a suitable weather shield for the hole made in the roof. It is, of course, advantageous to evacuate the super-heated air in the attic during the summer months, since it is quite common that temperatures in certain parts of the United States may reach up to 160.degree. F. in the attic space. Regardless of the amount and type of insulation employed in the attic, hot air will eventually penetrate through the insulation and cause the heat to build up in the living space. This ultimately causes an air conditioning system to operate for a longer length of time in an attempt to compensate for this heat or, in the event that no air conditioning is present, the living space will quickly become quite unpleasant.
However, in many sections of the country the temperature does not remain warm all year long and in fact quite frequently drops to at least below freezing in 75% of the country. Such conventional attic ventilation systems are then, of course, not usable during these cold months. Typically what happens during the winter months is that the moisture laden air inside the attic will cause ice to build up both inside and outside the attic. The ice build up inside the attic creates several problems since it typically forms on rafters and on any metallic parts such as nails, nail plates, or the like. Moreover, in temperate zones where the temperature during the winter does not stay below freezing but periodically goes to freezing and then rises to a relatively warmer daytime temperature, after a period of several cycles of such freezing and defrosting of the ice accumulation on the roofing nails, the expansion and contraction of the ice will loosen the roofing nails to such an extent that their holding power is minimized. Additionally, as the ice melts inside the attic, the water droplets cause additional problems since they may fall either onto the bare ceiling floor or onto insulation placed in the attic floor. Of course, should the insulation become wet or damp its effectiveness and life are considerably shortened. Furthermore, if the moisture is absorbed in the wood of the attic it may lead to rot, peeling paint, cracking plaster, and the like.